Automated cutting machines are well known for use in cutting from webs of cloth and other sheet material pieces used in the manufacture of clothing, upholstery and the like, the pieces usually being subsequently joined by sewing or other seaming processes to other pieces or components to complete a finished article of clothing or other product. Typical examples of such cutting machines are shown by U.S. Pat. Nos. 3,495,492, 3,955,458, 4,643,061, 4,646,911 and 4,841,822.
In such machines the sheet material to be cut is spread on a supporting surface, either as a single layer or as a layup of multiple layers, and is cut by a powered cutting knife driven in a cutting motion relative to the supporting surface and also moved along desired lines of cut relative to the supporting surface by a positioning system controlled by an associated controller responsive to cutting instructions input to the controller from a record medium such as a magnetic tape or disc or from some other data source. The cutting knife may be a circular one having a circular cutting edge and which for its cutting motion is rotated about its central axis, but more usually it is one elongated along a longitudinal axis, arranged generally perpendicularly to the supporting surface, having a sharp cutting edge extending along a longitudinal portion thereof, and which for its cutting motion is reciprocated along its longitudinal axis. The reciprocating knife, during its cutting operation, extends through the material being cut and with its lower end passes beyond the bottom surface of the work material and penetrates into the material forming the supporting surface or into some suitable receiver. To allow for such penetration, the supporting surface may, for example, be made as a bed of vertically extending bristles, and at the same time the bristle bed may be used as part of a vacuum system for applying a vacuum to the bottom surface of the material to be cut to aid in holding it to the supporting surface and in compacting it into a better condition for cutting; and in the latter case a sheet of air impermeable material may be spread over the work material to enhance the compressing effect achieved by the vacuum.
It is well known that in the use of automatic cutting machines of the aforementioned type the cutting knives become dull after relatively short periods of use and must frequently be sharpened to maintain acceptable cutting performance. The frequency of required sharpenings depends on the composition and height of the material being cut, as well as on other factors, but in an exemplary case the knife may have to be sharpened at about every thirty inches of cut. During each sharpening procedure the cutting operation is stopped, and the procedure lasts for at least several seconds until cutting is resumed. Accordingly, the frequent sharpenings substantially prolong the time required for cutting a given marker or set of patterns from the sheet material. Also, the sharpening is usually performed by grinding processes which during each sharpening procedure remove a substantial amount of the knife material thereby shortening the service life of the knife.
The general object of the invention is therefore to provide a knife for use in an automatically controlled machine for cutting cloth and the like which knife retains an acceptably sharp cutting edge longer and requires sharpenings much less frequently than the blades heretofore used in such machines.
A further object of the invention is to provide a knife of the afore-described type in combination with an associated sharpener and sharpening method whereby the cutting edge of the knife may be restored to acceptable sharpness after having become dulled despite the hard and tough nature of the blade material and without removing an excessive amount of such material, thereby allowing the knife to have a very much longer service life than the knives previously used with automatic cloth cutting machines.
Other objects and advantages of the invention will be apparent from the following description of the preferred embodiments of the invention and from the accompanying drawings and claims.